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Hybrid cartridge material

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: auxiliary » Mon Aug 31, 2009 5:30 pm

Instead of using schrader valves, I have the option of using a 1/8" tube to 3/8" NPT adapters as a fill/check valve. This fitting can just be threaded into place. They are rated to 230psi. These adapters have the female quick connector tube that can be used to fill the gun. As for a check valve, I can get a o-ring+nail to seal the other end and with a screwed-in perforated disc
I can hold the spring in. The advantage of this design is no epoxy is needed and it is cheaper.

Here are two more designs:

The second cartridge is an idea where no burst disk is used and the gas is held in by the friction and seal of the ammo. I think that ceramic slugs dipped in wax might work for this
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Last edited by auxiliary on Tue Sep 01, 2009 12:15 am, edited 1 time in total.
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Unread postAuthor: Mr.Sandman » Mon Aug 31, 2009 7:57 pm

auxiliary wrote:
Here are two more designs:

The second cartridge is an idea where no burst dick
haha burst dick. Watch out for those kinds of typos. Maybe look at BACH for more ideas. It seems to work kinda well.
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Unread postAuthor: THUNDERLORD » Mon Aug 31, 2009 11:48 pm

john bunsenburner wrote:Really the shells can be as complex as they are mode seeing as how they, once built, last along time.
To solve the problem you could have a non self ejecting shells, and stickign an end cap of some sort behind them.


The shrader internals will probably melt after a few firings.
If they are "non self ejecting" that is contrary to the OP.
So what is your point?
Besides that if they are non-ejecting, why use pre-charged shells in the first place?
What advantage would that have over a fueled chamber hybrid anyhow???

John bunsenburner: I know you are wearing only your red longjohn's again while reading SpudFiles....don't lie, I know you are! :P
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Unread postAuthor: auxiliary » Tue Sep 01, 2009 12:18 am

Oops... fixed it? I plan on making a prototype to see if any of my ideas work and from there, I will decide if the cartridges are capable of being used in an ejecting system.
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Unread postAuthor: john bunsenburner » Tue Sep 01, 2009 10:30 am

Because imagin how damn hot a bolt action hybrid woudl be with shells?
Also how come my typos are always there where I have been quoted?

And sharders are irt cheap if not free, if you have to replace them after every 5 shots thats no problem...

How about heatin up your shell and putting an oversized projectile in, that should solve the "bursk disk problem", no?
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Unread postAuthor: auxiliary » Tue Sep 01, 2009 8:46 pm

Thunderlord: I don't think that the schraders would melt after a few shots because once a cartridge is fired, it has at least five minutes (more like an hour) to cool down before it is refueled, loaded and shot.

John Bunsenburner: With the adapter set up, I believe it will be stronger than epoxying a schrader in so cost isn't the main issue. If I had to replace schraders every 5 shots I would not use them anyways.
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Unread postAuthor: THUNDERLORD » Wed Sep 02, 2009 8:50 am

Yeah, they might not melt, but it looks like a bunch of heat and pressure will be more focused at them than other designs.

If you could find shraders cheap enough, and the metal type dust caps,
Maybe the shrader with metal dust cap (drop o' lead inside cap) could blow out of threads as the projectile?

I found This link here Interesting for a Co2 cart. burst-disc cartridge design.
except, my version was not as complicated...
I simply chopped one end large enough to accept an automotive shrader,
chopped other side for burst-disc installation (couple washers that fit snug).
Maybe you could use 12 or 8 gram cart.s, using a plug and tube,with burst disc , AND ignition wires (or nichrome?) on one end,
And the shrader for filling on other.

If the plug had set screws holding it in place, they'd be re-useable.

The whole concept seems pretty dangerous if the burst material failed to burst at proper pressure, and with a snug fit rather than burst-disc, it could pop-off randomly or fail to become "un-snug" at proper moment.
(been interested in testing hot-glue though)

BTW, if the entire cartridge launches, no need for ejection.(?) 8)
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Unread postAuthor: daccel » Fri Sep 04, 2009 10:03 pm

Sorry, long post. Making up for being away :D.

Yeah BACH worked, but it was more form than function. Mainly due to fueling and ignition, though, so perhaps that's not fair to the cannon. Though fueling will always be more challenging at small volumes.

Fwiw, before I moved onto single chamber piston designs, I came to the conclusion that a direct blow-back breech would be easier to construct than an extracting bolt (though both are cool in their own right). And because I don't have access to aluminum tubing thick enough to tap, just copper pipe, that using pins as Moonbogg suggested or set screws to hold either end was the way to go. Though I was thinking of washers rather than aluminum plate, but that could work better.

Your burst disk could also be held by a washer retained by pins/screws, rather than inserting a fitting or making a custom union. If the ends of these were pointed, they would act as wedges when inserted to compress the disk retainer. Just need an oring or rubber washer behind.

I figured a custom check valve would be better than a schrader in a small cartridge where space is at a premium. You could also then design it with greater clearance between contacts, because if you're running a high mix that increased the resistance inside, it could short outside.

Another challenge is the cartridge - breech fit, unless you luck out and find something compatible. It has to virtually seal because you don't have a lot of volume to waste, but still slide easily. And especially important when using thin walled tube for cartridge. Last thought on that was to either layer telescopic brass tubing until it was thick enough, or drill out a rod. Though I pulled apart an air hammer recently, it has a nice thick steel cylinder that could possibly be adapted? Kind of short though, so might need a tube attached to the end that the cartridge would only pass through under low pressure at end of blow-back.

Edit: spelling
Edit2: picture of air hammer cylinder/piston, for $25 has potential? Need to find tube with correct OD though, in this case .75".
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 04, 2009 11:51 pm

Reminds me of some similar concepts I dreamt up in the past:

Image

The burst disk is the issue really, I came up with this as a purely pneumatic concept but the custom nature of the cartriges would have made it an expensive venture.

Still a complex undertaking, my last thoughtscentred around using oxygen to avoid the burst disk complication but never got round to getting a bottle.
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Unread postAuthor: inonickname » Fri Sep 04, 2009 11:55 pm

As a note with oxygen. You run into oxygen problems, which are much worse than burst disk problems. Not really recommended unless you know exactly what you're doing.
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 04, 2009 11:57 pm

inonickname wrote:You run into oxygen problems, which are much worse than burst disk problems.


One of the reasons this project was quietly shelved ;)
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Unread postAuthor: THUNDERLORD » Wed Sep 09, 2009 9:48 pm

...The burst disk is the issue really,...


I was daydreaming on a glass burst-disc for these the other day.
Glass can hold pressure, just not sudden shock so well.
I was thinking of those little paperwieght pieces that are flat and rounded other side at first,
but with some study, a weighed amt. of glass could be melted in a tube/mold.
Other advantage, the piece retaining it could be a small ring of epoxy or similar (much less restriction). 8)
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Unread postAuthor: Moonbogg » Wed Sep 09, 2009 11:11 pm

inonickname wrote:As a note with oxygen. You run into oxygen problems, which are much worse than burst disk problems. Not really recommended unless you know exactly what you're doing.


What problems? There are plenty of people out there who have used oxygen for fuel mixing without any issues.
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Unread postAuthor: ramses » Thu Sep 10, 2009 6:22 pm

john bunsenburner wrote:Also how come my typos are always there where I have been quoted?


When the forum quotes, it just copy/pastes whatever you said with the appropriate tags. It doesn't make a "Link" to whatever post you made, therefore changing the quoted text when you edit your post. It also allows people to make it look like a user said something they didn't ex:
john bunsenburner wrote:blah, blah, blah, something you don't want people to know you said, blah, blah, blah.




THUNDERLORD wrote:
...The burst disk is the issue really,...


I was daydreaming on a glass burst-disc for these the other day.
Glass can hold pressure, just not sudden shock so well.
I was thinking of those little paperwieght pieces that are flat and rounded other side at first,
you could also epoxy cut microscope cover slips on.
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Unread postAuthor: THUNDERLORD » Fri Sep 11, 2009 1:37 pm

...you could also epoxy cut microscope cover slips on....


Thought of those too, but seem thinner than what I envisioned.

I forgot to mention that if glass BD's were cast, the projectile, could be cast with the form, and the glss base would simply shatter and blow out, while the glass "bullet" retains form...The disadvantage is that the glass could scratch up even a nice barrel and also that the BD would produce (lower velocity) secondary projectiles in random patterns...

Hence a new (better?) idea!!!:
If the cartridges were made of copper pipe (or possibly aluminum),
Holes could be drilled in the tip of tubing,
Lead would be melted in the tip and melt into the holes in copper tubing.
A tube cutter (type with cutting wheel and bolt used for plumbing HVAC etc.)...
The cutting depth set a (little shallow?) would cut a groove at lead filled base (with a small copper skirt area?)
The copper or aluminum pipe fits into a barrel with same ID as the OD of the cartridge...
When fired, the entire lead filled tip of cart. breaks off at the cut groove...
8) 8) 8) (any questions?)
EDIT:LINKY of similar tool in mind
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